Even on those scorching, 100-degree-plus days when your look can best be described as least-amount-of-clothing-possible with a side of frizz, you can keep your cool with two things: a good manicure and a good pedicure (OK, and maybe also a braid). Here, the 45 nail colors you need to look polished all summer long.

In the world of nontoxic nail polish, three-free polishes (meaning formulas that contain no formaldehyde, toluene, or dibutyl phthalate) used to be the gold standard. But then we started wising up to other potentially harmful ingredients, like formaldehyde resin, camphor, ethyl tosylamide, and xylene. To help clarify what it means to be five-, seven-, eight-, and nine-free, we broke down our favorite new nontoxic nail polishes to tell you exactly what they're missing (in a good way!)

Besides the obvious—don't pick your cuticles or bite your nails, apply hand cream religiously, don't saw a file back and forth—there's one tip for better, healthier nails you may be missing. And it involves...